1

### NEET 2021

The right option for the statement "Tyndall effect is exhibited by", is :
A
Urea solution
B
NaCl solution
C
Glucose solution
D
Starch solution

## Explanation

$\bullet$ Tyndall effect is exhibited by colloidal solution only.

$\bullet$ Among the given options, Urea, NaCl and Glucose solutions are true solutions, so cannot show Tyndall effect.

$\bullet$ Starch solution is a colloidal solution therefore can show Tyndall effect.
2

### NEET 2020 Phase 1

Measuring Zeta potential is useful in determining which property of colloidal solution?
A
Solubility
B
Stability of the colloidal particles
C
Size of the colloidal particles
D
Viscosity

## Explanation

In colloidal solution, the potential difference between the fixed layer and the diffused layer of opposite charge is known as Zeta potential. The presence of equal and similar charges on colloidal particles are largely responsible in providing stability to the colloidal solution.
Zeta potential $\propto$ Stability of colloidal particle
3

### NEET 2018

On which of the following properties does the coagulating power of an ion depend?
A
The magnitude of the charge on the ion alone
B
Size of the ion alone
C
Both magnitude and sign of the charge on the ion
D
The sign of charge on the ion alone

## Explanation

According to Hardy Schulze rule :
1. Coagulation of colloidal solution by using an electrolyte depends on the charge present (positive or negative) on colloidal particles as well as on its size.
2. Coagulating power of an electrolyte depends on the magnitude of charge present on effective ion of electrolyte.
4

### NEET 2017

Which one of the following statements is not correct?
A
The value of equilibrium constant is changed in the presence of a catalyst in the reaction at equilibrium.
B
Enzymes catalyse mainly bio-chemical reactions.
C
Coenzymes increase the catalytic activity of enzyme.
D
Catalyst does not initiate any reaction.

## Explanation

A catalyst accelerates the forward and backward reaction to the same extent thus, the equilibrium constant does not change. Catalyst only speed up the reactions to attain equilibrium faster and does not alter equilibrium constant. Equilibrium constant varies only when temperature condition of reaction gets changed.